Extrinsic and intrinsic fiber connections of the telencephalon in a teleost, Sebastiscus marmoratus

Abstract

Extrinsic and intrinsic fiber connections of the telencephalic subdivisions of Nieuwenhuys ('62) in a teleost, Sebastiscus marmoratus, were studied by means of horseradish peroxidase (HRP) and Fink-Heimer methods. The olfactory bulb projects bilaterally to area dorsalis pars posterior, area ventralis pars ventralis, pars lateralis, pars posterior, pars intermedia, and the nucleus posterior tuberis of Peter et al. ('75) and receives fibers from ipsilateral area dorsalis pars centralis, pars posterior, area ventralis pars dorsalis, and pars supracommissuralis. Area dorsalis pars posterior sends numerous fibers to the ipsilateral ventral region of area dorsalis pars medialis, from which fibers of the medial forebrain bundle arise and terminate in the inferior lobe and nucleus posterior tuberis. Area dorsalis pars lateralis, pars dorsalis, and the dorsal region of pars medialis are the main targets of extratelencephalic ascending afferents. Area dorsalis pars lateralis receives fibers from the ipsilateral nucleus prethalamicus of Meader ('34), where tectal projections terminate massively. Area dorsalis pars dorsalis and the dorsal region of pars medialis receive afferents from the ipsilateral nucleus preglomerulosus of Schnitzlein ('62), nucleus posterior tuberis, area preoptica pars medialis of Crosby and Showers ('69), and nucleus entopeduncularis of Sheldon ('12). Raphe nuclei and locus ceruleus project bilaterally to area dorsalis pars centralis, pars dorsalis, pars lateralis, and the dorsal region of pars medialis. Area dorsalis pars centralis, pars dorsalis, and the dorsal region of pars medialis are important sources of extratelencephalic efferents. These subdivisions give rise to the lateral forebrain bundle and project to the ipsilateral nucleus prethalamicus, nucleus preglomerulosus, inferior lobe, nucleus paracommissuralis of Ito et al. ('82), optic tectum, torus semicircularis, and the bilateral mesencephalic tegmentum. Within the telencephalon, most of the ventral subdivisions project to ipsilateral area dorsalis pars centralis, pars dorsalis, pars lateralis, and the dorsal region of pars medialis. Area dorsalis pars centralis has reciprocal connections with ipsilateral area dorsalis pars lateralis, pars dorsalis, pars posterior, and the dorsal region of pars medialis. A dorsal part of the anterior commissure is composed of axons of the ventral region of area dorsalis pars medialis destined to the contralateral ventral region of area dorsalis pars medialis. A ventral part of the anterior commissure contains axons of area dorsalis pars centralis destined to contralateral area dorsalis pars lateralis.